The invention relates to a low pressure feeder, such as a device to be used to feed a metered amount of particulate material entrained in fluid from a low pressure area to a slightly higher pressure area. The feeder separates the high and low pressure areas while providing for the transfer of particulate material from one area to the other. Typical installations in which such feeders are utilized are in the pulp and paper field (such as between a chips bin and a steaming vessel), and in the coal and ore handling field (such as for feeding coal to a fluidized bed reactor).
The low pressure feeder according to the present invention has many features in common with the feeder disclosed in co-pending application Ser. No. 296,245 filed Aug. 24, 1981, the disclosure of which is hereby incorporated by reference herein. The feeder according to the present invention is simpler than the feeder disclosed in said co-pending application, however, and has a number of operational advantages.
The feeder according to the present invention requires only one shoe means providing a sealing means between a rotor and housing comprising the feeder. The shoe means has an opening communicating with the housing inlet port and in sealed engagement therewith. Also means are provided for biasing the shoe means into engagement with the rotor, and such means comprise improved pressure compensators operatively connected up to process pressure (e.g. the pressure at the housing outlet port). In one embodiment of the pressure compensators, a small amount of lubricating oil is supplied between the shoe means and the rotor, proper venting of any gas which might collect in the pressure compensator (as during start-up) is provided, and the pressure compensator is operable even after substantial wear of the shoe means.
The feeder according to the invention is advantageous in that the access opening of the at least one rotor pocket may, and does, communicate at the same time with a vent and inlet port. This ensures complete venting of the pocket while it is being filled. The action of the particulate material flowing into the pocket facilitates venting, ensuring a full charge in the pocket.
The feeder according to the invention is also advantageous in that a blast of gas at a pressure substantially higher than the pressure at the outlet port is supplied to the interior of the pocket when the access opening is in communication with the outlet port. This ensures discharge of the particulate material from the pocket even when the pressure at the outlet port is relatively high.
It is the primary object of the present invention to provide a simple, effective feeding device to feed a metered amount of particulate material entrained in fluid from a low pressure area to a slightly higher pressure area. This and other objects of the invention will become clear from an inspection of the detailed description of the invention and from the appended claims.